'03 196 throttle cable; coming loose at the PP motor

[78LS2]

My throttle cable keeps coming loose at the Perfect Pass motor. It is connected OK at the throttle body, but it keeps unspooling as I work the throttle arm at the helm. If I wind the knob back up on the PP, everything is OK for a while..until it loosens back up. How I do I keep it from unspooling?

Thanks!